Eleven years ago, a cave-in on the north side of a mine trapped six miners. Six days later, rescue teams found five dead miners and the comatose Harry Warden (Richard John Walters), who survived by killing the other miners with a pickaxe. Tom Hanniger, the mine owner's son, was blamed for the mine disaster because he forgot to vent the methane lines.
The following year on Valentine's Day, Warden wakes from his coma and kills many people. At the abandoned mineshaft that was the site of the disaster, a party is in full swing, attended by many teens, including Axel Palmer (Kerr Smith), his girlfriend, Irene (Betsy Rue), Tom Hanniger (Jensen Ackles), and his girlfriend, Sarah (Jaime King). Sarah goes in alone and gets lost looking for Axel and Irene. She runs across a teen and a few seconds later he is killed. She is confronted by Warden in full miner's garb, carrying a bloody pickaxe, and she flees. Axel grabs her and they, along with Irene, hide from the killer. Warden eventually sees the trio, and they run out of the mine, meeting Tom as he comes in. The killer hits Tom with the pickaxe, injuring him, while the other three run for the car and leave Tom behind. Tom runs back...